Mitsunari Tokugawa is the elderly owner and operator of the Underground Arena located beneath the Tokyo Dome, a venue where martial artists of any style engage in no-holds-barred combat. He belongs to a prominent and wealthy noble lineage, with his family's fortune accumulated over centuries, allowing him to finance and organize the arena's tournaments purely out of personal passion. Although extremely small in stature, standing around 150 centimeters tall and weighing about 45 kilograms, he is not a fighter himself. Instead, he possesses an encyclopedic knowledge of martial arts techniques, capable of identifying even obscure fighting styles and strategies. He has the final authority over every battle held in his arena and occasionally bends or breaks his own rules if doing so will intensify a match, once going so far as to threaten one of his own doctors with a knife to prevent a fight between Baki Hanma and Jack Hanma from being stopped. His deep admiration for martial arts and his respect for the fighters who step into his arena drive his actions, and at times he acts as a mentor or adviser to Baki and other combatants. Tokugawa maintains close friendships with Doppo Orochi and the fighter Igari, and has a strained but mutually aware acquaintance with the world's strongest creature, Yujiro Hanma. He is one of the very few individuals ever to outmaneuver Yujiro; when Yujiro attempted to disrupt a tournament, Tokugawa ordered hidden snipers to hit him with a tranquilizer dose strong enough to subdue a blue whale, temporarily rendering the unbeatable fighter unconscious. His strategic cunning and willingness to use underhanded methods to preserve the integrity of his matches are among his most notable traits, compensating for his lack of personal combat ability. Throughout the story, Tokugawa remains a constant behind-the-scenes presence, facilitating events, recruiting opponents, and ensuring that the strongest fighters in the world have a stage on which to test themselves.